1// Copyright 2019 The Prometheus Authors
2// Licensed under the Apache License, Version 2.0 (the "License");
3// you may not use this file except in compliance with the License.
4// You may obtain a copy of the License at
5//
6// http://www.apache.org/licenses/LICENSE-2.0
7//
8// Unless required by applicable law or agreed to in writing, software
9// distributed under the License is distributed on an "AS IS" BASIS,
10// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11// See the License for the specific language governing permissions and
12// limitations under the License.
13
14package procfs
15
16import (
17	"fmt"
18	"io/ioutil"
19	"net"
20	"strings"
21)
22
23// ARPEntry contains a single row of the columnar data represented in
24// /proc/net/arp.
25type ARPEntry struct {
26	// IP address
27	IPAddr net.IP
28	// MAC address
29	HWAddr net.HardwareAddr
30	// Name of the device
31	Device string
32}
33
34// GatherARPEntries retrieves all the ARP entries, parse the relevant columns,
35// and then return a slice of ARPEntry's.
36func (fs FS) GatherARPEntries() ([]ARPEntry, error) {
37	data, err := ioutil.ReadFile(fs.proc.Path("net/arp"))
38	if err != nil {
39		return nil, fmt.Errorf("error reading arp %q: %w", fs.proc.Path("net/arp"), err)
40	}
41
42	return parseARPEntries(data)
43}
44
45func parseARPEntries(data []byte) ([]ARPEntry, error) {
46	lines := strings.Split(string(data), "\n")
47	entries := make([]ARPEntry, 0)
48	var err error
49	const (
50		expectedDataWidth   = 6
51		expectedHeaderWidth = 9
52	)
53	for _, line := range lines {
54		columns := strings.Fields(line)
55		width := len(columns)
56
57		if width == expectedHeaderWidth || width == 0 {
58			continue
59		} else if width == expectedDataWidth {
60			entry, err := parseARPEntry(columns)
61			if err != nil {
62				return []ARPEntry{}, fmt.Errorf("failed to parse ARP entry: %w", err)
63			}
64			entries = append(entries, entry)
65		} else {
66			return []ARPEntry{}, fmt.Errorf("%d columns were detected, but %d were expected", width, expectedDataWidth)
67		}
68
69	}
70
71	return entries, err
72}
73
74func parseARPEntry(columns []string) (ARPEntry, error) {
75	ip := net.ParseIP(columns[0])
76	mac := net.HardwareAddr(columns[3])
77
78	entry := ARPEntry{
79		IPAddr: ip,
80		HWAddr: mac,
81		Device: columns[5],
82	}
83
84	return entry, nil
85}
86